The burglars were sophisticated, studying alarm systems and sawing into vaults from above before walking out of jewelry stores with loot that totaled in the millions.

They had a routine, hitting as many as 30 stores and often targeting South Asian jewelers, whose items have a higher gold content than other sellers, investigators said.

But their biggest heist, a $6 million job in Houston, led to their demise.

The Houston Police Department and FBI on Tuesday announced the arrests of two suspects who had allegedly operated gold businesses as fronts while they analyzed their own security systems, burglarized jewelry shops and used their own store equipment to dismantle and melt their earnings. A third suspect remains at large.

The arrests came after a seven-month investigation of jewelry heists in Houston, Dallas, Oklahoma and Florida over more than a decade. The search was accelerated by a key piece of evidence: an uncommon circular saw blade.

"We're certainly glad to apprehend them, and we're glad to put an end to the ring," said HPD Sgt. Frank Quinn, one of the lead investigators. "Getting to know the complainants and seeing the losses that they suffered makes you anxious to catch them."

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The group had targeted South Asian stores because jewelry from that part of the world uses a more pure form of gold, with 22-karat offerings more common in those stores than others where 14-karat pieces are more frequent, Quinn said. The high-quality gold meant that melting and selling the goods, particularly while gold prices have skyrocketed during the recession, made it attractive to the group.

All three have been charged with engaging in organized criminal activity. Each has been convicted of other crimes. The suspects had developed a tactic of cutting into jewelry vaults from store roofs, evading surveillance cameras.

Most of their materials were basic - saws and ladders were used, among other tools - and it was not clear if the group employed any advanced equipment to match the stealth nature of their capers.

Officials had no strong leads on the team for years, during which the group amassed luxury items that were eventually seized by law enforcement. Among them: a Mercedes, Range Rover, Cabin Cruiser and a $500,000 house. One suspect had also bought heavy duty cranes, which were seized from a crane company.

In the group's most prominent heist - a 10-hour overnight operation that occurred Feb. 5 in Houston - they cut into the roof of Karat 22 Jewelers in the 5600 block of Hillcroft, making only one hole in a spot of the roof where security cables and alarm wiring would be easy to avoid, said Aku Patel, the store's owner.

They evaded an interior camera, finding a way to shut it off before they entered its view and began stealing their loot from small safes and drawers, Patel said.

Then they sawed their way out of the vault from the inside, cutting through steel bars and eventually exiting from a back door of the shop, Quinn said.

Clue breaks the case

But the burglars had left behind a discarded circular saw blade, he said. Investigators learned the blade was only sold by Home Depot, and there had been several other cases of similar burglaries concentrated in Dallas and Houston, leading officials to focus on those areas.

They found that one man had made multiple purchases of blade packs, an extension ladder and work gloves in Dallas on the day before the burglary at Karat 22 Jewelers.

Further evidence, including the license plate of a truck seen at the store and connections made between suspects based on their time served together in Tarrant County Jail for other crimes, led investigators to zero in on the trio, in the process discovering their three gold stores in the Dallas area, Quinn said.

After his $6 million loss, police told Patel they would not rest until they brought the perpetrators to justice.

"I thought that was maybe just a statement to please me, but actually they proved it, and they showed that they've done an excellent job," Patel said.